Cyclic olefin copolymers (COC) are generally known as polymers that include a saturated cyclic moiety as part of the polymer, using monomers such as cyclobutene, cyclopentene, and norbornene (and typically, thus, styrene is not included within the definition of a cyclic olefin). Traditionally COC's are made using Ziegler-Natta polymerization (see U.S. Pat. No. 5,087,677) or, more recently, using metallocene catalysts (see U.S. Pat. No. 6,316,560). The most common type of COC in commercial production is one that incorporates norbornene as the cyclic olefin. Recently, there has been increased interest in copolymers of cyclopentene and other olefins, such as ethylene. Traditional Ziegler-Natta methods and catalysts, and metallocene catalysts, however, have been unable to polymerize cyclopentene and ethylene to produce a polymer having commercially desirable properties in a commercially acceptable process, and in particular have not produced a copolymer of cyclopentene and ethylene having a desirable glass transition temperature (Tg).
The Tg is an important property of cyclic olefin copolymers. Tg allows a measure of whether the material is more or less plastic or rubber, and is believed to reflect the ability of the polymer chain to move in the solid state. Many structural features of a polymer can affect the Tg, including chain flexibility, steric hindrance, side groups (presence, absence and/or size), symmetry, polarity and copolymerization. The Tg of known cyclic olefin copolymers is known to rise, generally, as the mole percent incorporation of the cyclic comonomer increases and lower Tg's result generally when fewer cyclic comonomer units are inserted into the chain. However, the Tg's of cyclic olefin copolymers produced from cyclopentene are generally low (Tg's well below 30° C. are common). See, e.g., LaVoie et al., Tetrahedron, Vol. 60 (2004), pp. 7147-7155; Fugita et al., Macromolecules, Vol. 35 (2002), pp. 9640-9647. What is needed is a catalyst capable of inserting cyclopentene monomer into the resulting polymer chain at a higher mole percentage than is known.
Ziegler-Natta catalysis, metallocene catalysis or other polymerization methods (e.g., ring opening metathesis) have not produced a cyclic olefin copolymer that includes cyclopentene having a desired microstructure or Tg. For example, metallocene catalysts produce copolymers of cyclopentene and ethylene where the cyclopentene is incorporated with a 1,3 insertion and/or with a low Tg. See Jerschow et al., Macromolecules, 1995, Vol. 28, pp. 7095-7099. Also for example, ring-opening metathesis polymerization produces a maximum of 50 mole % cyclopentene in the copolymers, and without direct bonding of the cyclopentene monomers in the product and without a commercially-desirable Tg. See Fugita et al. Macromolecules, Vol. 35 (2002) pp. 9640-9647.
Recently, work has been performed on olefin polymerization catalysts that move beyond metallocenes. For example, Symyx scientists have produced a variety of catalysts that do not rely on metallocenes for a variety of polymerization and other processes. See for example U.S. Pat. Nos. 6,869,904; 6,794,514; and 6,750,345. A need exists for a cyclic olefin copolymer with a high Tg made from cyclopentene, and also for such polymers to be prepared with non-cyclopentadienyl based catalysts.